Conduit to be embedded in existing concrete slab

Question

Conduit to be embedded in existing concrete slab

dannyypk (Structural)

(OP)

29 Jan 20 04:17

Running into a situation that the contractor would like to embed new electrical conduit into the existing elevated concrete slab ( 8" deep)

Any code section (ACI, NEC) has any requirements for the depth of the embedment?

JAE (Structural) · Answer 1 · 2020-01-29 05:03:04

So they want to saw cut a groove 8 in deep or something and install the conduit?

Is this a slab on grade or a suspended structural slab?

Ron (Structural) · Answer 2 · 2020-01-29 11:21:32

I would not recommend grooving an elevated slab for conduit installation. Is there any reason the conduit can't be installed on the bottom side of the slab and holes drilled where top access is needed?

Ingenuity (Structural) · Answer 3 · 2020-01-30 01:44:30

About 15 years ago we got called out to a high-end condo where the contractor was doing a single condo re-model, including re-routing electrical etc.

They cut and trenched the soffit of the suspended slab overhead which was precast, pre-tensioned slabs. They severed numerous 1/2" dia 7-wire strands at midspan.

Emergency shoring installed and some very upset upstairs neighbors. Expensive error by he contractor that got him banned from every doing work on that condo building too.

Photo I took of one strand that got off 'light' - they only partially severed a few wires of the strand.

Be very careful in allowing the 'chasing' of any structural element.

msquared48 (Structural) · Answer 4 · 2020-01-30 04:27:47

Just tell the contractor that he can demolish and reinstall the slab with the conduit in place if that would be acceptable to him...

Mike McCann, PE, SE (WA, HI)

skeletron (Structural) · Answer 5 · 2020-01-31 05:20:48

I've only dealt with this on a ground level slab-on-grade. Owner wanted to encase an electrical conduit coming out of ground and then running up the wall. I guess he thought it was an eyesore or a tripping hazard or something. I think in the end, because of geometry, they ended up with a big weird shaped blob of concrete in the island. Nothing more than a glorified bench/skateboard obstacle.

darthsoilsguy2 (Geotechnical) · Answer 6 · 2020-02-07 13:41:34

Why? If there is an ACI standard that addresses this, it was probably written under the assumption that the slab is new. Your questions seems too obscure for the committee to take up.

Sounds like this is a bid problem and not a structural problem. Did the electrician didn't carry rigid conduit for surface mount and wants to embed plastic and the GC is too weak to hold them to the bid docs, or the GC received a written proposal that was different from bid docs. If so the building shouldn't compromise its structure for contractor error.

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Conduit to be embedded in existing concrete slab